U.S. patent number 10,881,464 [Application Number 15/743,625] was granted by the patent office on 2021-01-05 for lower extremities leg length calculation method.
This patent grant is currently assigned to MAKO Surgical Corp.. The grantee listed for this patent is MAKO Surgical Corp.. Invention is credited to Daniel Odermatt, Matt Thompson.
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United States Patent |
10,881,464 |
Odermatt , et al. |
January 5, 2021 |
Lower extremities leg length calculation method
Abstract
A method of calculating leg length discrepancy of a patient
including: receiving patient bone data associated with a lower body
of the patient; identifying anatomical landmarks in the patient
bone data; orienting a first proximal landmark and a second
proximal landmark relative to each other and an origin in a
coordinate system; aligning a first axis associated with a first
femur and a second axis associated with a second femur with a
longitudinal axis extending in a distal-proximal direction, wherein
the first and second distal landmarks are adjusted according to the
alignment of the first and second axes; calculating a distance
between the first and second distal landmarks in the
distal-proximal direction along the longitudinal axis; and
displaying at least one of the distance or a portion of the patient
bone data on a display screen.
Inventors: |
Odermatt; Daniel (Fort
Lauderdale, FL), Thompson; Matt (Fort Lauderdale, FL) |
Applicant: |
Name |
City |
State |
Country |
Type |
MAKO Surgical Corp. |
Fort Lauderdale |
FL |
US |
|
|
Assignee: |
MAKO Surgical Corp. (Fort
Lauderdale, FL)
|
Family
ID: |
1000005280147 |
Appl.
No.: |
15/743,625 |
Filed: |
July 13, 2016 |
PCT
Filed: |
July 13, 2016 |
PCT No.: |
PCT/US2016/042129 |
371(c)(1),(2),(4) Date: |
January 10, 2018 |
PCT
Pub. No.: |
WO2017/011576 |
PCT
Pub. Date: |
January 19, 2017 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20180199995 A1 |
Jul 19, 2018 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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62191890 |
Jul 13, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B
6/505 (20130101); A61B 5/055 (20130101); A61B
90/50 (20160201); A61B 34/30 (20160201); A61B
6/5217 (20130101); A61B 34/10 (20160201); A61B
6/032 (20130101); A61B 34/20 (20160201); A61B
34/25 (20160201); A61B 8/00 (20130101); A61B
5/107 (20130101); A61B 2034/104 (20160201); A61B
2034/108 (20160201); A61B 2034/105 (20160201); A61B
17/1666 (20130101); A61B 8/5223 (20130101); A61B
8/0875 (20130101); A61B 2034/101 (20160201) |
Current International
Class: |
A61B
34/10 (20160101); A61B 17/16 (20060101); A61B
8/08 (20060101); A61B 90/50 (20160101); A61B
34/20 (20160101); A61B 8/00 (20060101); A61B
34/30 (20160101); A61B 34/00 (20160101); A61B
6/00 (20060101); A61B 5/055 (20060101); A61B
5/107 (20060101); A61B 6/03 (20060101) |
Field of
Search: |
;703/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Hofmann et al. (Minimizing Leg-Length Inequality in Total Hip
Arthroplasty: Use of Preoperative Templating and an Intraoperative
X-Ray, 2008, American journal of orthopedics) (Year: 2008). cited
by examiner .
Ogawa et al. (Accurate Leg Length Measurement in Total Hip
Arthroplasty: A Comparison of Computer Navigation and a Simple
Manual Measurement Device, 2014, The Korean Orthopaedic
Association) (Year: 2014). cited by examiner .
Subotnic et al . ("Limb Length Discrepancies of the Lower Extremity
(The Short Leg Syndrome)", JOSPT, 1981, pp. 11-16) (Year: 1981).
cited by examiner .
Woerman et al. ("Leg Length Discrepancy Assessment: Accuracy and
Precision in Five Clinical methods off Evaluation",JOSPT, 1984, pp.
230-239) (Year: 1984). cited by examiner .
Sabharwal et al. ("Methods for Assessing Leg Length Discrepancy",
Clin Orthop Relat Res (2008) pp. 2910-2922) (Year: 2008). cited by
examiner.
|
Primary Examiner: Khan; Iftekhar A
Attorney, Agent or Firm: Polsinelli PC
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This applications claims priority to and the benefit of U.S.
Provisional Patent Application No. 62/191,890, filed Jul. 13, 2015,
entitled "LOWER EXTREMITIES LEG LENGTH CALCULATION METHOD", which
is hereby incorporated by reference in its entirety.
This application incorporates by reference the following
applications in their entireties: U.S. patent application Ser. No.
12/894,071, filed Sep. 29, 2010, entitled "SURGICAL SYSTEM FOR
POSITIONING PROSTHETIC COMPONENT AND/OR FOR CONSTRAINING MOVEMENT
OF SURGICAL TOOL"; U.S. patent application Ser. No. 13/234,190,
filed Sep. 16, 2011, entitled "SYSTEMS AND METHOD FOR MEASURING
PARAMETERS IN JOINT REPLACEMENT SURGERY"; U.S. patent application
Ser. No. 11/357,197, filed Feb. 21, 2006, entitled "HAPTIC GUIDANCE
SYSTEM AND METHOD"; U.S. patent application Ser. No. 12/654,519,
filed Dec. 22, 2009, entitled "TRANSMISSION WITH FIRST AND SECOND
TRANSMISSION ELEMENTS"; U.S. patent application Ser. No.
12/644,964, filed Dec. 22, 2009, entitled "DEVICE THAT CAN BE
ASSEMBLED BY COUPLING"; and U.S. patent application Ser. No.
11/750,807, filed May 18, 2007, entitled "SYSTEM AND METHOD FOR
VERIFYING CALIBRATION OF A SURGICAL DEVICE".
Claims
We claim:
1. A computer program stored on one or more tangible,
non-transitory, computer-readable storage media having executable
instructions for performing the computer program on a computing
system, the computer program comprising: receiving patient bone
data having a first side and a second side, one of the first or
second sides including a degenerate or deformed condition;
generating a computer model of the first and second sides from the
patient bone data; identifying anatomical landmarks in the patient
bone data or the computer model, the anatomical landmarks
comprising: a first proximal point and a first distal point on the
first side; and a second proximal point and a second distal point
on the second side; orienting the first and second sides of the
computer model relative to each other in a coordinate system such
that: a pelvic axis extending through the first and second proximal
points are generally perpendicular to a longitudinal axis of the
first and second sides of the computer model; and a first axis
associated with a first femur and a second axis associated with a
second femur are generally parallel to the longitudinal axis;
calculating a leg length discrepancy based on the first and second
sides of the computer model after orienting the first and second
sides of the computer model relative to each other.
2. The computer program of claim 1, wherein the first proximal
point corresponds to a femoral head center of a first femur of the
first side of the patient bone data, and the second proximal point
corresponds to a femoral head center of a second femur of the
second side of the patient bone data.
3. The computer program of claim 1, wherein the first distal point
corresponds to a first point in or on a first bone in a first foot
region of the first side of the patient bone data, and the second
distal point corresponds to a second point in or on a second bone
in a second foot region of the second side of the patient bone
data.
4. The computer program of claim 1, further comprising: adjusting
an orientation of at least one of a first knee joint of the
computer model defined between a first femur and a first tibia of
the first side of the patient bone data or a second knee joint of
the computer model defined between a second femur and a second
tibia of the second side of the patient bone data.
5. The computer program of claim 1, wherein the patient bone data
comprises at least one of CT images, MR images, or X-ray
images.
6. The computer program of claim 1, wherein the leg length
discrepancy comprises determining a distance between the first and
second distal points in a direction of the longitudinal axis.
7. The computer program of claim 1, wherein the leg length
discrepancy comprises determining a difference between a first
distance and a second distance, the first distance defined between
the first proximal point and the first distal point on the first
side, the second distance defined between the second proximal point
and the second distal point on the second side.
Description
TECHNICAL FIELD
The present disclosure relates generally to surgical methods used
in orthopedic joint replacement surgery and, more particularly, to
methods of lower extremities leg length calculations.
BACKGROUND
Robotic systems are often used in applications that require a high
degree of accuracy and/or precision, such as surgical procedures or
other complex tasks. Such systems may include various types of
robots, such as autonomous, teleoperated, and interactive.
Interactive robotic systems may be preferred for some types of
surgery, such as joint replacement surgery, because they enable a
surgeon to maintain direct, hands-on control of the surgical
procedure while still achieving a high degree of accuracy and/or
precision. For example, in knee replacement surgery, a surgeon can
use an interactive, haptically guided robotic arm in a passive
manner to sculpt bone to receive a joint implant, such as a knee
implant. To sculpt bone, the surgeon manually grasps and
manipulates the robotic arm to move a cutting tool (e.g., a
rotating burr) that is coupled to the robotic arm to cut a pocket
in the bone. As long as the surgeon maintains a tip of the burr
within a predefined virtual cutting boundary or haptic boundary
defined, for example, by a haptic object, the robotic arm moves
freely with low friction and low inertia such that the surgeon
perceives the robotic arm as essentially weightless and can move
the robotic arm as desired. If the surgeon attempts to move the tip
of the burr to cut outside the virtual cutting boundary, however,
the robotic arm provides haptic feedback (e.g., forced resistance)
that prevents or inhibits the surgeon from moving the tip of the
burr beyond the virtual cutting boundary. In this manner, the
robotic arm enables highly accurate, repeatable bone cuts. When the
surgeon manually implants a knee implant (e.g., a patellofemoral
component) on a corresponding bone cut the implant will generally
be accurately aligned due to the configuration of and interface
between the cut bone and the knee implant.
The above-described interactive robotic system may also be used in
hip replacement surgery, which may require the use of multiple
surgical tools having different functions (e.g., reaming,
impacting), different configurations (e.g., straight, offset), and
different weights. A system designed to accommodate a variety of
tools is described in U.S. patent application Ser. No. 12/894,071,
filed Sep. 29, 2010, entitled "SURGICAL SYSTEM FOR POSITIONING
PROSTHETIC COMPONENT AND/OR FOR CONSTRAINING MOVEMENT OF SURGICAL
TOOL", which is hereby incorporated by reference in its
entirety.
During a hip replacement surgery, as well as other robotically
assisted or fully autonomous surgical procedures, the patient bone
is intra-operatively registered with a corresponding virtual or
computer bone model to correlate the pose (i.e., position and
rotational orientation) of the actual, physical bone with the
virtual bone model. The patient bone (physical space) is also
tracked relative to the surgical robot, haptic device, or surgical
tool with at least one degree of freedom (e.g., rotating burr). In
this way, the virtual cutting or haptic boundaries controlled and
defined on the virtual bone model via a computer can be applied to
the patient bone (physical space) such that the haptic device is
constrained in its physical movement (e.g., burring) when working
on the patient bone (physical space).
During a hip replacement procedure, a surgeon may attempt to
correct a patient's leg length discrepancy (LLD), which is a
difference in the length of the right and left leg, either caused
by a true length discrepancy of one or more bones or a misalignment
of one or more joints. The use of an accurate and reliable
algorithm to assess LLD before and during surgery is important for
planning and executing precision total hip replacement.
Conventional imaging methods for measuring LLD involve measuring
the distance between a pelvic reference (e.g., inter-ischial, tear
drop line) and another reference on the proximal or distal femurs.
Other conventional methods involve using tape measures and standing
blocks to asses LLD pre or post-operatively. Intra-operatively, LLD
is typically measured manually by palpating the distal femurs or
malleoli with the patient supine and the legs in line with the
shoulders. Most of these methods have limitations and may not
provide reliable measurements of LLD. Thus, there is an opportunity
to use pre-operative imaging such as but not limited to computed
tomography (CT) data from the pelvis, knees and lower extremities
to develop a reliable, repeatable algorithm for LLD measurement
that accounts for the full length of the leg.
SUMMARY
Aspects of the present disclosure involve a method of calculating
leg length discrepancy of a patient. In certain instances, the
method may include receiving patient bone data associated with a
lower body of the patient, the lower body includes a first side and
a second side, the first side includes a first portion of a pelvis,
a first femur, a first tibia, and a first distal extremity, the
second side includes a second portion of the pelvis, a second
femur, a second tibia, and a second distal extremity. In certain
instances, the method may further include identifying anatomical
landmarks in the patient bone data, the anatomical landmarks
includes a first proximal landmark and a first distal landmark
associated with the first side and a second proximal landmark and a
second distal landmark associated with the second side. In certain
instances, the method may further include orienting the first
proximal landmark and the second proximal landmark relative to each
other and an origin in a coordinate system. In certain instances,
the method may further include aligning a first axis associated
with the first femur and a second axis associated with the second
femur with a longitudinal axis extending in a distal-proximal
direction, the first and second distal landmarks may be adjusted
according to the alignment of the first and second axes. In certain
instances, the method may further include calculating the leg
length discrepancy based on a first distance between the first
proximal landmark and the first distal landmark and a second
distance between the second proximal landmark and the second distal
landmark. In certain instances, the method may further include
displaying at least one of the leg length discrepancy or a portion
of the patient bone data on a display screen.
In certain instances, the first axis may include a first femoral
mechanical axis, and the second axis may include a second femoral
mechanical axis.
In certain instances, the first axis and the second axis may be
aligned parallel to the longitudinal axis.
In certain instances, the first and second proximal landmarks
remain in an unchanged orientation relative to the origin when the
first and second axes are aligned relative to the longitudinal
axis.
In certain instances, the longitudinal axis may be defined as a
normal vector to a pelvic axis extending through the first and
second proximal landmarks.
In certain instances, the first proximal landmark may be associated
with a first location on the first portion of the pelvis, and the
second proximal landmark may be associated with a second location
on the second portion of the pelvis.
In certain instances, the first tibia and the first distal
extremity have a first alignment relative to the first femur that
may be unchanged when the first and second axes may be aligned, the
second tibia and the second distal extremity have a second
alignment relative to the second femur that may be unchanged when
the first and second axes may be aligned.
In certain instances, further includes adjusting at least one of
the first alignment or the second alignment so as to adjust a
condition at a knee joint.
In certain instances, the condition may be a valgus or valrus
deformity.
In certain instances, the condition may be a flexed or extended
knee joint.
In certain instances, further includes generating a three
dimensional bone model of the first side and the second side from
the patient bone data.
In certain instances, the patient bone data may include medical
images of the lower body of the patient.
In certain instances, the medical images were generated from a
medical imaging machine includes at least one of a CT scanner, MRI
machine, ultrasound scanner, or X-ray machine.
In certain instances, the patient bone data may be captured via at
least one of an intra-operative bone scanner, a digitizer, or a
navigated ultrasound probe.
In certain instances, the first distal extremity may be a first
talus bone, and the second distal extremity may be a second talus
bone.
In certain instances, calculating the leg length discrepancy may
include determining a difference between the first and second
distances in the distal-proximal direction.
In certain instances, calculating the leg length discrepancy may
include determining a distance between the first and second distal
landmarks in the distal-proximal direction.
Aspects of the present disclosure involve a method of calculating
leg length discrepancy of a patient body including a first side and
a second side, the first side including a first portion of a
pelvis, a first femur, a first tibia, and a first foot region, the
second side including a second portion of the pelvis, a second
femur, a second tibia, and a second foot region. In certain
instances, the method may include receiving patient bone data
associated with the first and a second sides of the patient body,
one of the first or second sides including a degenerate or deformed
condition, the patient bone data having been generated by a medical
imaging device. In certain instances, the method may further
include generating a computer model of the first and second sides
of the patient body from the patient bone data. In certain
instances, the method may further include identifying anatomical
landmarks in the patient bone data or the computer model, the
anatomical landmarks includes: a first proximal point and a first
distal point on the first side; and a second proximal point and a
second distal point on the second side. In certain instances, the
method may further include orienting the first and second sides of
the computer model relative to each other in a coordinate system
such that: a pelvic axis extending through the first and second
proximal points may be generally perpendicular to a longitudinal
axis of the first and second sides of the computer model; and a
first axis associated with the first femur and a second axis
associated with the second femur may be generally parallel to the
longitudinal axis. In certain instances, the method may further
include calculating the leg length discrepancy based on the first
and second sides of the computer model after orienting the first
and second sides of the computer model relative to each other. In
certain instances, the method may further include displaying at
least one of the leg length discrepancy or a portion of the
computer model on a display screen.
In certain instances, the first proximal point corresponds to a
femoral head center of the first femur, and the second proximal
point corresponds to a femoral head center of the second femur.
In certain instances, the first distal point corresponds to a first
point in or on a first bone in the first foot region, and the
second distal point corresponds to a second point in or on a second
bone in the second foot region.
In certain instance, further includes: adjusting an orientation of
at least one of a first knee joint of the computer model defined
between the first femur and the first tibia or a second knee joint
of the computer model defined between the second femur and the
second tibia.
In certain instances, the patient bone data may include at least
one of CT images, MR images, or X-ray images.
In certain instances, the leg length discrepancy may include
determining a distance between the first and second distal points
in a direction of the longitudinal axis.
In certain instances, the leg length discrepancy may include
determining a difference between a first distance and a second
distance, the first distance defined between the first proximal
point and the first distal point on the first side, the second
distance defined between the second proximal point and the second
distal point on the second side.
Aspects of the present disclosure involve a method of calculating
leg length discrepancy of a lower body of a patient includes a
pelvic region, femurs, tibias, and feet. In certain instances, the
method may include receiving patient bone data representative of at
least a portion of the lower body of the patient including the
pelvic region, femurs, tibias, and feet, the patient bone data
having been generated via a medical imaging device. In certain
instances, the method may further include generating computer
models of the lower body from the patient bone data, the computer
models including first and second side pelvic models, first and
second femur models, first and second tibia models, and first and
second foot models. In certain instances, the method may further
include orienting the first and second side pelvic models relative
to an origin in a coordinate system. In certain instances, the
method may further include orienting the first and second femur
models, first and second tibia models, and first and second foot
models relative to the first and second side pelvic models. In
certain instances, the method may further include adjusting an
orientation of one of the first and second femur models, first and
second tibia models, or first and second foot models with respect
to an anteroposterior or mediolateral axis. In certain instances,
the method may further include calculating the leg length
discrepancy based upon a difference in length between a first
landmark in the first foot model and a second landmark in the
second foot model in a direction of a longitudinal axis extending
from the first and second foot models to the first and second side
pelvic models. In certain instances, the method may further include
displaying at least one of the difference or a portion of the
computer models on a display screen.
In certain instances, the patient bone data may include at least
one of CT images, MR images, or X-ray images.
In certain instances, the first landmark may be a first point in or
on a talus bone of the first foot model, and the second landmark
may be a second point in or on a talus bone of the second foot
model.
In certain instances, the patient bone data may include information
associated with a statistical bone model.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a perspective view of a femur and a pelvis.
FIG. 1B is a perspective view of a hip joint formed by the femur
and pelvis of FIG. 1A.
FIG. 2A is an exploded perspective view of a femoral component and
an acetabular component for a total hip replacement procedure.
FIG. 2B is a perspective view illustrating placement of the femoral
component and acetabular component of FIG. 2A in relation to the
femur and pelvis of FIG. 1A, respectively.
FIG. 3A is a perspective view of an embodiment of a surgical
system.
FIG. 3B is a perspective view of an embodiment of a robotic arm of
the surgical system of FIG. 3A.
FIG. 4 illustrates an embodiment of a computer display for use
during a surgical procedure.
FIG. 5A illustrates an embodiment of steps of pre-operatively
planning a hip replacement procedure.
FIG. 5B illustrates an embodiment of steps of intra-operatively
performing a hip replacement procedure.
FIGS. 6 and 7 illustrate an embodiment of a pelvic registration
method shown on a display screen.
FIG. 8 is a flow chart describing a method for measuring leg length
discrepancy pre- and intra-operatively based on lower extremities
landmarks.
FIG. 9 is a front view of a user interface showing segmentation of
the talus bone.
FIG. 10 is a front view of a user interface showing acquisition of
the talus bone in a CT image.
FIG. 11A is a front view of a user interface showing the alignment
of the knees in the coronal plane in an un-adjusted manner.
FIG. 11B is a front view of a user interface showing the alignment
of the knees in the coronal plane in an adjusted manner.
FIG. 11C is another front view of a user interface showing the
alignment of the knees in the coronal plane in an adjusted
manner.
FIG. 11D is a front view of a user interface showing the alignment
of the knees in the coronal and sagittal planes.
FIG. 12A is a coronal view of a skeletal structure of a patient
with a pelvic tracking array in the pelvis and a femoral tracking
array in the femur prior to the resection of the femur.
FIG. 12B is a coronal view of a skeletal structure of a patient
with a pelvic tracking array in the pelvis and a femoral tracking
array in the femur following the resection of the femur and
implantation of a femoral and acetabular component of a hip
replacement system.
FIG. 12C is a coronal view of a skeletal structure of a patient
with a pelvic tracking array in the pelvis and distal extremity
points probed via a localizer device prior to resection of the
femur.
FIG. 12D is a coronal view of a skeletal structure of a patient
with a pelvic tracking array in the pelvis and distal extremity
points probed via a localizer device following the resection of the
femur and implantation of a femoral and acetabular component of a
hip replacement system.
FIG. 13 is an example computing system having one or more computing
units that may implement various systems and methods discussed
herein is provided.
DETAILED DESCRIPTION
I. Overview
The hip joint is the joint between the femur and the pelvis and
primarily functions to support the weight of the body in static
(e.g., standing) and dynamic (e.g., walking) postures. FIG. 1A
illustrates the bones of a hip joint 10, which include a left
pelvis 12 and a proximal end of a left femur 14. The proximal end
of the femur 14 includes a femoral head 16 disposed on a femoral
neck 18. The femoral neck 18 connects the femoral head 16 to a
femoral shaft 20.
As shown in FIG. 1B, the femoral head 16 fits into a concave socket
in the pelvis 12 called the acetabulum 22, thereby forming the hip
joint 10. The acetabulum 22 and femoral head 16 are both covered by
articular cartilage that absorbs shock and promotes articulation of
the joint 10. Over time, the hip joint 10 may degenerate (e.g., due
to osteoarthritis) resulting in pain and diminished functionality.
As a result, a hip replacement procedure, such as total hip
arthroplasty or hip resurfacing, may be necessary. During hip
replacement, a surgeon replaces portions of a patient's hip joint
10 with artificial components. In total hip arthroplasty, the
surgeon removes the femoral head 16 and neck 18 and replaces the
natural bone with a prosthetic femoral component 26 comprising a
head 26a, a neck 26b, and a stem 26c (shown in FIG. 2A). As shown
in FIG. 2B, the stem 26c of the femoral component 26 is anchored in
a cavity the surgeon creates in the intramedullary canal of the
femur 14. Alternatively, if disease is confined to the surface of
the femoral head 16, the surgeon may opt for a less invasive
approach in which the femoral head is resurfaced (e.g., using a
cylindrical reamer) and then mated with a prosthetic femoral head
cup (not shown). Similarly, if the natural acetabulum 22 of the
pelvis 12 is worn or diseased, the surgeon resurfaces the
acetabulum 22 using a reamer and replaces the natural surface with
a prosthetic acetabular component 28 comprising a hemispherical
shaped cup 28a (shown in FIG. 2A) that may include a liner 28b. To
install the acetabular component 28, the surgeon connects the cup
28a to a distal end of an impactor tool and implants the cup 28a
into the reamed acetabulum 22 by repeatedly striking a proximal end
of the impactor tool with a mallet. If the acetabular component 28
includes a liner 28b, the surgeon snaps the liner 28b into the cup
28a after implanting the cup 28a. Depending on the position in
which the surgeon places the patient for surgery, the surgeon may
use a straight or offset reamer to ream the acetabulum 22 and a
straight or offset impactor to implant the acetabular cup 28a. For
example, a surgeon that uses a postero-lateral approach may prefer
straight reaming and impaction whereas a surgeon that uses an
antero-lateral approach may prefer offset reaming and
impaction.
II. Exemplary Robotic System
A surgical system described herein may be utilized to perform hip
replacement, as well as other surgical procedures. As shown in FIG.
3A, an embodiment of a surgical system 5 for surgical applications
according to the present disclosure includes a computer assisted
navigation system 7, a tracking device 8, a computer 15, a display
device 9 (or multiple display devices 9), and a robotic arm 30.
The robotic arm 30 can be used in an interactive manner by a
surgeon to perform a surgical procedure on a patient, such as a hip
replacement procedure. As shown in FIG. 3B, the robotic arm 30
includes a base 32, an articulated arm 34, a force system (not
shown), and a controller (not shown). A surgical tool 58 (e.g., a
rotary burring device as seen in FIG. 3A, an end effector 40 having
an operating member as seen in FIG. 3B) is coupled to an end of the
articulated arm 34, and the surgeon manipulates the surgical tool
58 by grasping and manually moving the articulated arm 34 and/or
the surgical tool.
The force system and controller are configured to provide control
or guidance to the surgeon during manipulation of the surgical
tool. The force system is configured to provide at least some force
to the surgical tool via the articulated arm 34, and the controller
is programmed to generate control signals for controlling the force
system. In one embodiment, the force system includes actuators and
a backdriveable transmission that provide haptic (or force)
feedback to constrain or inhibit the surgeon from manually moving
the surgical tool beyond predefined virtual boundaries defined by
haptic objects as described, for example, in U.S. patent
application Ser. No. 11/357,197 (Pub. No. US 2006/0142657), filed
Feb. 21, 2006, and/or U.S. patent application Ser. No. 12/654,519,
filed Dec. 22, 2009, each of which is hereby incorporated by
reference herein in its entirety. In a certain embodiment the
surgical system is the RIO.RTM.. Robotic Arm Interactive Orthopedic
System manufactured by MAKO Surgical Corp. of Fort Lauderdale, Fla.
The force system and controller are preferably housed within the
robotic arm 30.
The tracking device 8 is configured to track the relative locations
of the surgical tool 58 (coupled to the robotic arm 30) and the
patient's anatomy. The surgical tool 58 can be tracked directly by
the tracking device 8. Alternatively, the pose of the surgical tool
can be determined by tracking the location of the base 32 of the
robotic arm 30 and calculating the pose of the surgical tool 58
based on joint encoder data from joints of the robotic arm 30 and a
known geometric relationship between the surgical tool and the
robotic arm 30. In particular, the tracking device 8 (e.g., an
optical, mechanical, electromagnetic, or other known tracking
system) tracks (or enables determination of) the pose (i.e.,
position and orientation) of the surgical tool and the patient's
anatomy so the navigation system 7 knows the relative relationship
between the tool and the anatomy.
In operation, a user (e.g., a surgeon) manually moves the robotic
arm 30 to manipulate the surgical tool 58 (e.g., the rotary burring
device, the end effector 40 having an operating member) to perform
a surgical task on the patient, such as bone cutting or implant
installation. As the surgeon manipulates the tool 58, the tracking
device 8 tracks the location of the surgical tool and the robotic
arm 30 provides haptic (or force) feedback to limit the surgeon's
ability to move the tool 58 beyond a predefined virtual boundary
that is registered (or mapped) to the patient's anatomy, which
results in highly accurate and repeatable bone cuts and/or implant
placement. The robotic arm 30 operates in a passive manner and
provides haptic feedback when the surgeon attempts to move the
surgical tool 58 beyond the virtual boundary. The haptic feedback
is generated by one or more actuators (e.g., motors) in the robotic
arm 30 and transmitted to the surgeon via a flexible transmission,
such as a cable drive transmission. When the robotic arm 30 is not
providing haptic feedback, the robotic arm 30 is freely moveable by
the surgeon and preferably includes a virtual brake that can be
activated as desired by the surgeon. During the surgical procedure,
the navigation system 7 displays images related to the surgical
procedure on one or both of the display devices 9.
To aid in tracking the various pieces of equipment within the
system, the robotic arm 30 may include a device marker 48 to track
a global or gross position of the robotic arm 30, a tool end marker
54 to track the distal end of the articulating arm 34, and a
free-hand navigation probe 56 for use in the registration process.
Each of these markers 48, 54, 56 (among others such as navigation
markers positioned in the patient's bone) is trackable by the
tracking device 8 with optical cameras, for example.
The computer 15 may include a display and an input device (e.g.,
keyboard, mouse) and is configured to communicate with the
navigation system 7, the tracking device 8, the various display
devices 9 in the system, and the robotic arm 30. Furthermore, the
computer 15 may receive information related to a particular
surgical procedure and perform various functions related to
performance of the surgical procedure. For example, the computer 15
may have software as necessary to perform functions related to
image analysis, surgical planning, registration, navigation, image
guidance, and haptic guidance. A more detailed analysis of an
example computing system having one or more computing units that
may implement various systems and methods discussed herein, is
described subsequently in reference to FIG. 14.
FIG. 3B depicts an end effector 40 particularly suited for use in
robotic assisted hip arthroplasty. The end effector 40 is
configured to be mounted to an end of the robotic arm 30. The end
effector 40 includes a mounting portion 50, a housing, a coupling
device, and a release member. The end effector 40 is configured to
individually and interchangeably support and accurately position
multiple operating members relative to the robotic arm 30. As seen
in FIG. 3B, the end effector 40 is coupled to an operating member
100. The end effector 40 and related tools, systems, and methods
are described in U.S. patent application Ser. No. 12/894,071, filed
Sep. 29, 2010, which is hereby incorporated by reference in its
entirety.
The mounting portion (or mount) 50 preferably couples the end
effector 40 to the robotic arm 30. In particular, the mounting
portion 50 extends from the housing and is configured to couple the
end effector 40 to a corresponding mounting portion 35 of the
robotic arm 30 using, for example, mechanical fasteners, such that
the mounting portions are fixed relative to one another. The
mounting portion 50 can be attached to the housing or formed
integrally with the housing and is configured to accurately and
repeatably position the end effector 40 relative to the robotic arm
30. In one embodiment, the mounting portion 50 is a semi-kinematic
mount as described in U.S. patent application Ser. No. 12/644,964,
filed Dec. 22, 2009, and hereby incorporated by reference herein in
its entirety.
The end effector 40 in FIG. 3B is one example of a surgical tool
that can be tracked and used by the surgical robotic arm 30. Other
tools (e.g., drills, burrs) as known in the art can be attached to
the robotic arm for a given surgical procedure.
III. Pre-operative Planning a Surgical Procedure
Referring to FIGS. 4 and 5A, a preoperative CT (computed
tomography) scan of the patient's pelvis 12 and femur 14 is
generated or obtained at step R1. The scan image may be generally
described as "patient data" or "patient bone data." Such patient
data may be generated with a medical imaging device (e.g., CT
scanner) prior to the surgical procedure. While the discussion will
focus on CT scans, other imaging modalities (e.g., MRI) may be
similarly be employed. Additionally and alternatively, X-ray images
derived from the CT scan and/or the three dimensional models 512,
514 can be used for surgical planning, which may be helpful to
surgeons who are accustomed to planning implant placement using
actual X-ray images as opposed to CT based models. The CT scan may
be performed by the surgeon or at an independent imaging facility.
Additionally or alternatively, intra-operative imaging methods may
be employed to generate a patient model of the bone. For example,
various boney surfaces of interest may be probed with a tracked
probe to generate a surface profile of the surface of interest. The
surface profile may be used as the patient bone model. Additionally
and alternatively, generic bone data or models (e.g., based on
statistical averages of a sample population) that are at least
partially representative of the patient's bone shape and lengths,
among other characteristics, may be used in place of or in addition
to patient data that is sampled from the actual patient bone. In
such an instance, a representative bone data set or model may be
selected or generated that approximates the lengths and conditions
of the actual patient bone. Accordingly, the present disclosure is
applicable to all methods of obtaining or generating patient bone
data and a patient bone model or a portion thereof.
As shown in FIG. 4 and at step R2 of FIG. 5A, the CT scan or data
from the CT scan is segmented and to obtain a three dimensional
model 512 of the pelvis 12 and a three dimensional model 514 of the
femur 14. At step R3, leg length discrepancy (LLD) is determined
prior to the surgery. Determining LLD pre-operatively is described
more fully in the subsequent paragraphs.
At steps R4 and R5 of FIG. 5A, the three dimensional models 512,
514 are used by the surgeon to construct a surgical plan at least
in part to correct LLD. The surgeon selects an implant at step R4
of FIG. 5A and selects a desired pose (i.e., position and
orientation) of the acetabular component and the femoral component
relative to the models 512, 514 of the patient's anatomy. For
example and as seen in FIG. 4, a planned pose 500 of the acetabular
cup can be designated and displayed on a computer display, such as
the display device 9. At step R5 of FIG. 5A, the various bone cuts
or resections may be determined based upon the desired pose of the
implant, among other possible factors.
It is noted that the pre-operatively planning may include a plan
for a knee arthroplasty procedure in addition to a hip arthroplasty
procedure. The knee arthroplasty procedure may be at the same time
as the hip procedure or at a later time. Either way, correction of
the LLD, among other deformities, may be in part due to the hip
arthroplasty procedure and in part from the knee arthroplasty
procedure. For example, the pre-operative planning may include a
present correction of a shorter femur in a hip arthroplasty
procedure while also planning for an eventual correction to a
varus/valgus knee deformity in a knee arthroplasty occurring
subsequent to the hip arthroplasty procedure.
A. Leg Length Calculation
In certain instances, LLD may be pre-operatively determined and
then compared with an intra-operative determination of LLD, which
will be discussed in subsequent sections of this application. In
certain instances, step R3 of determining pre-operative LLD may be
based on using anatomical information between the proximal femurs
and the lower extremities. Through imaging of the pelvis, knees,
ankles and feet, the method of determining LLD described herein can
be used to acquire information on the mechanical axes and use a
distal landmark such as, for example, the calcaneus or talus, among
other landmarks, to calculate LLD using the full length of the
legs. While conventional (manual surgical) methods typically rely
on subjective visual assessments of the knee positions, and
conventional computer-assisted surgical methods focus only on "hip
length" at the level of the greater or lesser trochanter or above,
the method described herein utilizes computer assisted surgical
systems and provides an LLD measurement that accounts for the full
length of the legs.
Referring back to step R1 of FIG. 5A and to step T1 of FIG. 8,
which depicts a flow diagram of a method of calculating and
correcting LLD, patient bone data or medical images of the pelvis,
proximal femur, knee, ankle, and foot may be pre-operatively
generated or obtained for both the affected and non-affected legs.
As stated previously, various imaging modalities may be utilized to
generate the patient bone data such as, for example, CT, MRI,
X-ray, or the like. The patient bone data may provide various
anatomical landmarks for calculating LLD pre- and
intra-operatively.
As shown in step R2 of FIG. 5A and step T2 of FIG. 8, a
three-dimensional patient bone model is generated from the patient
bone data via a segmentation process or otherwise. In certain
instances, a segmentation process may include outlining or
segmenting a boundary of a particular bone on each of a plurality
of image scans or slices in a certain plane (e.g., sagittal,
transverse, coronal). The segmenting of the image scans provides an
outline of points on the bone at discrete increments. The plurality
of image scans may be positioned adjacent to each other such that
there is a gap between each image scan that is equal to the scan
spacing (e.g., 2 mm) of the imaging machine. Generating the bone
model entails extrapolating a surface in the gap area between the
adjacent image slices so as to make a solid or surface model from
the plurality of spaced-apart and segmented image scans. While a
segmentation process is described herein, any known method of
generating the bone models may be used for the purposes of this
discussion.
At step T3 of FIG. 8, landmarks are selected in either the medical
images or the three dimensional patient bone models. More
particularly, the following anatomical landmarks may be selected or
identified for each leg: anterior-superior iliac spine (ASIS),
femoral head center, knee center, talus centroid. The list of
landmarks is not exhaustive and may include additional or different
landmarks without departing from the scope of the present
disclosure.
An illustrative example of identifying and selecting the talus
centroid can be seen in FIGS. 9 and 10. As seen in FIG. 9, which is
a display screen 9 illustrating patient bone data 600 in the form
of two dimensional images of a patient's foot 602 in various
planes, the talus bone 604 is segmented in the top-right image
along a bone boundary line 606 that separates the bone 604 from the
surrounding tissue 608. A user may segment the individual slices of
the talus bone 604, for example, in this view. The views of the
talus bone 604 on the top-left, bottom-left, and bottom-right
illustrate coronal, transverse, and sagittal views, respectively,
and each view illustrates a user selecting a center point 610 of
the talus bone 604 with cross-hairs movable via a cursor, for
example. Since the talus bone 604 is three-dimensional in physical
space, the centroid or center of mass 612, as seen in FIG. 10, may
be determined by identifying the center point 610 in the coronal,
transverse, and sagittal views of the two dimensional images 602,
as shown in FIG. 9.
Upon completing the segmentation process for the talus bone 604 as
shown in FIG. 9, the system 5 may generate the three dimensional
bone model 614 of the talus bone 604, as well as other segmented
bones of the foot, as seen in the top-right of FIG. 10. As seen in
the top-left, bottom-right, and bottom-left views of FIG. 10, the
illustrations are the same as those shown in FIG. 9. Locational
information pertaining to the position of the centroid 612 may be
stored within the three dimensional bone model 614.
In certain instances, calculating LLD may be done without
generating three dimensional bone models of the various bones
described herein. That is, the anatomical landmarks may be
identified in the image data (e.g., CT, MRI, X-ray), and
coordinates (e.g., x, y, z) associated with the identified
landmarks may be used for calculating LLD without generating a 3D
surface model of the bones.
And while the talus bone 604 is referenced herein as a distal or
lower extremity landmark, other bones at or near the foot (e.g.,
navicular, calcaneus) or other landmarks of the talus (e.g., most
distal aspect of the talus) may be used for purposes of calculating
LLD without departing from the teachings of the present
disclosure.
While segmentation and identification of landmarks is only shown
for the talus bone 604, segmentation and three dimensional bone
model generation may continue for the each of the two dimensional
images of the pelvis 12, femur 14, and tibia 13, as described in
any of the applications incorporated by reference. In certain
embodiments, the anatomical landmarks may be selected or identified
in the two dimensional medical images or the three dimensional bone
model for the femur head centers and knee centers, as shown at step
T3 of FIG. 8, in a similar manner as described with reference to
the talus bone 604 in FIGS. 9 and 10.
At step T4 of FIG. 8, the three dimensional bone models of the
femur, tibia, and talus 514, 513, 614, together referred to as a
patient bone model in an unadjusted state 650 and an adjusted state
652, are displayed on a display screen 9 and the femoral models 514
of the patient bone models 650, 652 are aligned relative to a
longitudinal or vertical axis VA of the pelvis, as seen in FIG.
11A. In certain instances, as seen in FIG. 11D, the three
dimensional bone model of the pelvis 624 may be used in the
calculation and may be used to define a pelvic axis PA, for
example, as extending medial-lateral across opposite points on the
pelvis. The pelvic axis PA may be used to define the longitudinal
or vertical axis VA of the pelvis as being a normal vector of the
pelvic axis PA.
In certain instances, the femoral head centers 616 of the right and
left femurs of the patient bone models 650, 652 may be parallel to
the pelvic axis PA (extending in a medial-lateral direction). In
this case, the proximal femurs of the right and left legs are fixed
relative to each other such that LLD may be determined at a distal
anatomical landmark such as the talus bone, which provides an LLD
calculation that encompasses the entire lengths of the legs.
In certain instances, the femoral models 514 may be aligned
relative to the vertical axis VA, but not otherwise fixed or
"zeroed" relative to each other at the pelvic axis PA (i.e., the
right and left femoral head centers may be at different elevations
on along the vertical axis VA). While right and left proximal
femurs whose femoral head centers 616 are parallel with the pelvic
axis PA allows for a length measurement to be determined only by
the difference at the distal extremities (as noted by the distance
D1 in FIGS. 11B and 11C), the distance D1 may also be found by
measuring the entire length of each leg from a proximal landmark
(e.g., ASIS, tear-drop, inferior ischial, femoral head center) to a
distal landmark (e.g., talus centroid, distal aspect of talus or
tibia), and determining the difference in length D1 between the
right and left legs. In this way, the proximal landmarks may be at
different elevations on the vertical axis VA (i.e., not parallel to
the pelvic axis) and a measure of LLD may be found. While the
disclosure includes reference to a determination of leg length
between the distal landmarks of a right and left leg, other
measurements may be used, such as those described in this paragraph
and others, to measure the difference in leg length between the
right and left legs.
In certain instances and as seen in FIG. 11D, the pelvic model 624
may be used to define the coordinate system of the pelvic axis PA
and the longitudinal or vertical axis VA, and the other bone models
(e.g., femur, tibia, talus) may be oriented relative to the pelvic
model 624. In such instances, the pelvic axis PA may be defined by
identifying and selecting opposite points on the pelvic model 624
and defining an axis through the points. For example and as shown
in FIG. 11D, the ASIS 625 may be selected (at step T3 of FIG. 8) on
a right and left side of the pelvic model 624, and a line (the
pelvic axis PA) may extend through the right and left ASIS 625.
Once the pelvic axis PA is defined from the pelvic model 624, the
longitudinal or vertical axis VA may be defined as a normal vector
of the pelvic axis PA.
Once the vertical axis VA is defined, the femoral mechanical axes
FMA of the femur models 514 may be aligned with the vertical axis
VA of the pelvis, at step T4 of FIG. 8. It is noted, the femur and
pelvic models 514, 624 may be joined together such that aligning of
the pelvic model 624 with the pelvic axis PA may cause the femur
models 514 to move accordingly within the coordinate system. For
example, the center of the acetabulum may be used as a common point
between the pelvic and femur models 624, 514 to join the models
relative to each other, while allowing the femur model 514 to
rotate about the center of acetabulum. In this way, once the pelvic
model 624 is aligned relative to the pelvic axis PA, the femur
model 514 is free to rotate about the center of acetabulum, but is
restricted from translating within the coordinate system.
Aligning the pelvic model 624 in the medial-lateral direction via
the selected points on, for example, the ASIS and defining the
pelvic axis PA in this way allows for consideration of cartilage
degeneration, and other factors, at the hip joint that may cause a
perceived discrepancy in leg length even if the length of the right
and left legs are the same. For example, a right hip joint of a
patient may be normal with a healthy amount of cartilage at the
joint and a left hip joint may be diseased with very little
cartilage present in the joint. The patient may perceive a shorter
left leg because of the difference in cartilage at the left hip
joint despite the right and left legs being the same length. In
such an instance, if femoral points were used to define the pelvic
axis PA, as opposed to points on the pelvic model 624, the right
and left legs may measure as equal when, in this example, there is
degeneration at the joint that causes a perception of leg length
discrepancy.
Referring back to FIGS. 11A-11C, while the pelvic model 624 is not
displayed, the femoral head centers 616 are shown relative to a
pelvic axis PA that may be defined based on selected points (e.g.,
ASIS) on the pelvic model 624. As seen in FIG. 11A, other
deformities, such as those at the knee (e.g., varus/valgus
deformities), may remain unadjusted at this point. Adjustment of
the knee deformities, for example via a knee arthroplasty and its
effect on LLD, will be addressed subsequently.
Upon defining the pelvic axis PA and longitudinal or vertical axis
VA, described previously, the mechanical axes of the femur models
514 of the affected (right side) and unaffected side (left side)
are aligned to be parallel with the vertical axis VA, as described
in step T4 of FIG. 8 and as seen in FIGS. 11A and 11B. Adjustment
of the femoral and tibial mechanical axes can be seen in FIG. 11B,
which illustrates a display screen 9 showing an adjusted bone model
652, with adjustments made at the hip and knee region. The bone
models 650, 652 both include the femur, tibia, and talus bone
models 514, 513, 614 and the identified femoral head centers 616,
knee centers 618, and talus centroids 612. The femoral mechanical
axis FMA is defined between the femoral head center 616 and the
knee center 618. The tibial mechanical axis TMA is defined between
the knee center 618 and the talus centroid 612.
As seen in FIG. 11A, the un-adjusted bone model 650 represents a
valgus knee 620 on the right and a normal knee 622 on the left. The
mechanical axes FMA, TMA of the valgus knee 620 are offset and
non-parallel to each other and to the vertical axis VA, whereas the
mechanical axes FMA, TMA of the normal knee 622 are generally
parallel to each other and the vertical axis VA. Upon aligning the
femoral mechanical axes FMA with the vertical axis, the bone model
652 will appear as shown in FIG. 11B (which also shows a correction
of the valgus knee joint).
In certain instances, the system 5 may use the identified
anatomical landmarks as end points associated with the femoral and
tibial mechanical axes FMA, TMA, and the system 5 may display the
bone models of the femur, tibia, and talus bones 514, 513, 614 in
the same orientation as the patient was positioned during an image
scan (e.g., CT). In certain instances, an adjustment of the right
and left femur models may cause the tibia and talus models to move
accordingly while maintaining their original orientation relative
to the femur models. In this way, a knee deformity may not be
corrected by the initial adjustment of the right and left femur
models to be parallel to the vertical axis. In certain instances,
the system or surgeon may correct or adjust the orientation of the
tibia and talus models relative to the femur so as to correct or
adjust a knee or ankle deformity.
At steps T5 and T6 of FIG. 8, the femoral and tibial mechanical
axes FMA, TMA, among other parameters including varus/valgus
deformities, flexion/extension angles of the knee, among others,
can be identified, and adjusted or fixed by the system 5 and
displayed on the display screen 9.
The surgeon may view the bone model 650 in FIG. 11A in various
views to calculate knee deformities, as seen in step T5 of FIG. 8.
For example, varus/valgus deformities may be seen in a coronal
view, as depicted in FIG. 11A, whereas flexion/extension angles may
be seen in a sagittal view (not shown).
At step T6 and as seen in FIG. 11B, the system 5 may allow a user
(e.g., surgeon) to set values for the femoral and tibial mechanical
axes FMA, TMA relative to each other or the vertical axis VA to
correct varus/valgus deformities, flexion/extension of the knee,
and other parameters, such that the three dimensional bone models
of the femur, tibia, and talus 514, 513, 614 will be moved
according to the inputted values. In this way, the surgeon may
virtually align both the affected (right side in FIG. 11A) and
non-affected (left side in FIG. 11A) sides of the patient's body in
a similar manner (e.g., with both affected and non-affected sides
having zero degrees mechanical axis) so LLD may be pre-operatively
determined or calculated, regardless of the orientation of the
patient's body during the acquisition of two dimensional
images.
Thus, as seen in FIG. 11B, the system 5 has adjusted the formerly
valgus knee 620 by aligning the femoral and tibial mechanical axes
FMA, TMA to be generally parallel with each other and the vertical
axis VA. In this way, both knees 620, 622 match each other with
regard to femoral and tibial mechanical axes FMA, TMA. Adjustment
of the valgus knee may be in anticipation of a knee arthroplasty
procedure at the same time as the hip procedure or at another time
as part of an effort to correct LLD at the hip and knee.
In certain instances, as seen in FIG. 11C, which is a coronal view
of an adjusted bone model 652 displayed on a display screen 9, a
surgeon may not adjust the valgus knee on the right, but, upon
adjusting the mechanical axis FMA of the femur model 514 to be
parallel with the vertical axis VA, the surgeon may leave the
orientation of the femur relative to the tibia unadjusted.
In certain instances, as seen in step T7 of FIG. 8, the system 5
may pre-operatively calculate LLD as the distance D1 between the
talus centroids 612 as measured relative to the vertical axis VA.
More particularly and as seen in FIGS. 11B and 11C, LLD may be
measured as the distance D1, along the vertical axis VA, between a
first perpendicular line P1 intersecting a first talus centroid 612
and a second perpendicular line P2 intersecting a second talus
centroid 612. As discussed previously, the distance D1 may be
calculated by measuring the length of the entire right and left
legs and calculating the difference. For example, each of the right
and left legs may be measured from the pelvic axis (e.g., right and
left ASIS) to the talus centroid 612, and the difference between
the right and left legs will yield the distance D1.
In this way, an LLD calculation is made by virtually aligning the
bone models 650, 652 that will be representative of the patient's
physical body following a hip and/or a knee arthroplasty procedure.
Using a distal anatomical landmark such as the talus bone provides
an LLD calculation that encompasses the entire lengths of the legs
as opposed to conventional methods, which focus on only the
proximal femur. And by including information from the pelvis, such
as using the pelvic axis PA as defined through points (e.g., ASIS)
on the pelvis, allows for an LLD calculation that captures
potential degeneration at the joint as well as other deformities of
the leg(s).
It is also noted that while the embodiment in FIGS. 11A-11C do not
show the pelvic model 624, in certain instances, as seen in FIG.
11D, a three dimensional bone model 624 of the pelvis 12 may be
depicted on the display screen 9 along with the bone models of the
femur, tibia, and talus 514, 513, 614. As seen in FIG. 11D, which
is a front view of a display screen 9 showing the bone models 514,
513, 614, a surgeon may set values for varus deformities 626 and
extension 628 at the knee. Upon setting the values, the hip length
or LLD is displayed 630 accordingly. In the embodiment in FIG. 11D,
the un-adjusted bone model 650 and adjusted bone model 652 may be
combined to show only a single bone model 650, 652 that is adjusted
according to the set values or not adjusted if the values are
unmodified.
At step T9 of FIG. 8, the surgeon pre-operatively plans the hip
replacement procedure to correct the LLD as determined from step
T7. During this step, the surgeon may select an implant and
determine the position and orientation of the implant to correct
the LLD, as seen in step R4 of FIG. 5A. Selection of the implant
and determination of the pose of the implant may influence the
determination of the bone cuts or resections to perform on the
bones (e.g., proximal femur, acetabulum), as seen in step R5 of
FIG. 5A. For example, implant stem length may be a factor to
consider to lengthen or shorten the length of the femur to
compensate for a particular LLD deformity.
It is noted that in certain instances, patient data may be captured
via a localizer tool (e.g., digitizer, navigated ultrasound probe)
by a surgeon just prior to or during the surgical procedure. In
such instances, the patient data obtained from the localizer tool
may take the place of obtaining pre-operative images (e.g., CT,
MRI, X-ray) at step T1, of FIG. 8, and generating a 3D bone model
at step T2, also of FIG. 8. The localizer tool may gather
information about a particular bone such as surface contour
information, rotational information (e.g., center of rotation), or
location data associated with certain anatomical landmarks. The
gathered information may be used by the system 5 to calculate
mechanical axes (e.g., FMA, TMA) and develop a model with which to
calculate and adjust deformities, at step T5 and T6 of FIG. 8.
The remaining portions of the intra-operative procedure will be
discussed in the following sections.
IV. Intra-Operative Procedures
During the surgical procedure and referring back to FIG. 3A, motion
of the patient's anatomy and the surgical tool in physical space
are tracked by the tracking device 8, and these tracked objects are
registered to corresponding models in the navigation system 7
(image space). As a result, objects in physical space are
correlated to corresponding models in image space. Therefore, the
surgical system 5 knows the actual position of the surgical tool
relative to the patient's anatomy and the planned pose 500 (as seen
in FIG. 4), and this information is graphically displayed on the
display device 9 during the surgical procedure.
A. Tracking and Registration of Femur
FIG. 5B illustrates an embodiment of intra-operative steps of
performing a total hip replacement. In this embodiment, steps
S1-S12 may be performed with or without the robotic arm 30. For
example, step S8 (reaming) can be performed using robotic arm 30
with the end effector 40 coupled to the operating member 100 or the
operating member 200, and step S10 (impacting) can be performed
using the robotic arm 30 with the end effector 40 coupled to the
operating member 300 or the operating member 400.
In step S1 of the surgical procedure, as seen in FIG. 12A, which is
a coronal view of a patient's skeletal structure to undergo a hip
arthroplasty procedure, a cortical tracking array 632 is attached
to the femur 14 to enable the tracking device 8 to track motion of
the femur 14. In step S2, the femur 14 is registered (using any
known registration technique) to correlate the pose of the femur 14
(physical space) with the three dimensional model 514 of the femur
14 in the navigation system 7 (image space). Additionally, the
femur checkpoint is attached. In step S3, the femur 14 is prepared
to receive a femoral implant (e.g., the femoral component 26) using
a navigated femoral broach.
B. Tracking and Registration of Pelvis
In step S4 of FIG. 5B, a pelvic tracking array 634 is attached to
the pelvis 12 to enable the tracking device 8 to track motion of
the pelvis 12, as seen in FIG. 12A. In step S5, a checkpoint is
attached to the pelvis 12 for use during the surgical procedure to
verify that the pelvic tracking array has not moved in relation to
the pelvis 12. The checkpoint can be, for example, a checkpoint as
described in U.S. patent application Ser. No. 11/750,807 (Pub. No.
US 2008/0004633), filed May 18, 2007, and hereby incorporated by
reference herein in its entirety.
In step S6, the pelvis 12 is registered to correlate the pose of
the pelvis 12 (physical space) with the three dimensional model 512
of the pelvis 12 in the navigation system 7 (image space). In
certain embodiments, as shown in FIG. 6, registration is
accomplished using the tracked navigation probe 56 to collect
points on the pelvis 12 (physical space) that are then matched to
corresponding points on the three dimensional model 512 of the
pelvis 12 (image space). Two methods of registering the three
dimensional model 512 of the pelvis (image space) and the pelvis 12
(physical space) are described in the subsequent sections of this
application.
As shown in FIG. 6, the display device 9 may show the
representation 512 of the pelvis 12, including one or more
registration points 516. The registration points 516 help the
surgeon understand where on the actual anatomy to collect points
with the tracked probe. The registration points 516 can be color
coded to further aid the surgeon. For example, a registration point
516 on the pelvis 12 to be collected next with the tracked probe
can be colored yellow, while registration points 516 that have
already been collected can be colored green and registration points
516 that will be subsequently collected can be colored red. After
registration, the display device 9 can show the surgeon how well
the registration algorithm fit the physically collected points to
the representation 512 of the pelvis 12.
For example, as shown in FIG. 7, error points 518 can be displayed
to illustrate how much error exists in the registration between the
surface of the representation 512 and the corresponding surface of
the physical pelvis 12. In one embodiment, the error points 518 can
be color coded, for example, with error points 518 representing
minimal error displayed in green and error points 518 representing
increasing amounts of error displayed in blue, yellow, and red. As
an alternative to color coding, error points 518 representing
different degrees of error could have different shapes or sizes.
Verification points 519 can also be displayed. The verification
points 519 illustrate to the surgeon where to collect points with
the tracked probe to verify the registration. When a registration
point 519 is collected, the software of the navigation system 7
displays the error (e.g., numerically in millimeters) between the
actual point collected on the anatomy and the registered location
of the representation 512 in physical space. If the registration
error is too high, the surgeon re-registers the pelvis 12 by
repeating the registration process of step S6.
C. Registering of Robotic Arm
Referring back to FIG. 5B, after registering the pelvis at step S6,
the robotic arm 30 may be registered at step S7. In this step, the
robotic arm 30 is registered to correlate the pose of the robotic
arm 30 (physical space) with the navigation system 7 (image space).
The robotic arm 30 can be registered, for example, as described in
U.S. patent application Ser. No. 11/357,197 (Pub. No. US
2006/0142657), filed Feb. 21, 2006, and hereby incorporated by
reference herein in its entirety.
D. Preparation of the Acetabulum and Performance of the Surgical
Procedure
In operation, the surgeon can use the robotic arm 30 to facilitate
a joint replacement procedure, such as reaming bone and implanting
an acetabular cup for a total hip replacement or hip resurfacing
procedure. As explained above, the robotic arm 30 includes a
surgical tool configured to be coupled to a cutting element (for
reaming) and to engage a prosthetic component (for impacting). For
example, for reaming, the end effector 40 can couple to the
operating member 100 or the operating member, each of which couples
to the cutting element. Similarly, for impacting, the end effector
40 can couple to the operating member or the operating member, each
of which engages the prosthetic component. The robotic arm 30 can
be used to ensure proper positioning during reaming and
impacting.
In step S8 of FIG. 5B, the surgeon resurfaces the acetabulum 22
using a reamer, such as the operating member 100, coupled to the
robotic arm 30. As described above in connection with the operating
member 100, the surgeon couples the appropriate operating member
(e.g., a straight or offset reamer) to the end effector 40,
connects the cutting element to the received operating member, and
manually manipulates the robotic arm 30 to ream the acetabulum 22.
During reaming, the robotic arm 30 provides haptic (force feedback)
guidance to the surgeon. The haptic guidance constrains the
surgeon's ability to manually move the surgical tool to ensure that
the actual bone cuts correspond in shape and location to planned
bone cuts (i.e., cuts consistent with the surgical plan).
In step S9 of FIG. 5B, the surgeon verifies that the registration
(i.e., the geometric relationship) between the acetabular tracking
array and the pelvis 12 is still valid by contacting the pelvis
checkpoint with a tracked probe as described, for example, in U.S.
patent application Ser. No. 11/750,807 (Pub. No. US 2008/0004633),
filed May 18, 2007, and hereby incorporated by reference herein in
its entirety. If registration has degraded (e.g., because the
acetabular tracking array was bumped during reaming), the pelvis 12
is re-registered. Registration verification can be performed any
time the surgeon wants to check the integrity of the acetabular
registration.
In step S10 of FIG. 5B, the prosthetic component 316 is implanted
on the reamed acetabulum 22 using an impactor tool. In a manner
identical to that described above in connection with step S8
(reaming), during the impaction step S10, the display device 9 can
show the planned pose 500, the activation region 510, the
representations 512, 514 of the anatomy, and a representation of
the surgical tool. Also as described above in connection with step
S8, if the surgeon moves the end effector 40 to override the haptic
feedback, the controller can initiate automatic control of the
surgical tool to substantially align at least one aspect of the
actual pose with the corresponding desired aspect of the target
pose.
E. Leg Length Calculation
In step S11 of FIG. 5B, the surgeon installs the femoral component
on the femur 14. Next, in step S12 of FIG. 5B and step T11 of FIG.
8, the surgeon determines leg length and femoral offset. At any
time during the surgical procedure, the display device 9 can show
data related to progress and/or outcome. For example, after reaming
in step S8 and/or impacting in step S10), data relating to the
actual position of the reamed acetabulum 22 (or the implanted
acetabular cup) can include, for example, numerical data
representing error between the actual and planned locations in the
three orthogonal planes of the patient's anatomy (i.e.,
medial/lateral, superior/inferior, and anterior/posterior).
In certain instances, step S12 of FIG. 5B and step T11 of FIG. 8
for determining leg length discrepancy (LLD) may include comparing
the pre-operatively determined LLD with an intra-operative
measurement of LLD.
In certain instances, intra-operative LLD may be determined by
based on the position of the femoral and pelvic tracking arrays
634, 632, as seen in FIGS. 12A and 12B. FIG. 12A depicts a coronal
view of a patient's skeletal structure including the pelvis 12,
femur 14, and knee joint 10 with a pelvic tracking array 634
positioned in the pelvis 12 and a femoral tracking array 632
positioned in the femur 14 prior to the resection of the proximal
femur including the femoral neck and head 18, 16. FIG. 12B depicts
a coronal view of a patient's skeletal structure including the
pelvis 12, femur 14, and knee joint 10 with a pelvic tracking array
634 positioned in the pelvis 12 and a femoral tracking array 632
positioned in the femur 14 following the resection of the proximal
femur and implantation of femoral and acetabular components of a
hip implant system 636.
Upon registering the pelvis 12 and the femur 14 via the pelvic
tracking array 634 and the femoral tracking array 632, the system 5
may calculate a first value or distance D10 between the tracking
arrays 634, 632 in a given pose(s) (i.e., position and orientation)
of the femur 14 relative to the pelvis 12. For example, the surgeon
may position the patient's femur 14 such that the femoral
mechanical axis (not shown in FIG. 12A) is parallel to the vertical
axis (not shown in FIG. 12A). In certain instances, the surgeon may
use the tracking ability of the system 5 to verify that the femur
14 is positioned in the correct pose relative to the pelvis 12 for
determining the distance D20.
Following the hip replacement procedure where the proximal femur is
resected and replaced with a femoral component that is positioned
within an acetabular component, as seen in FIG. 12B, the surgeon
may calculate a second value or distance D20 between the tracking
arrays 634, 632 in a given pose(s) of the femur 14 relative to the
pelvis 12. In certain instances, the pose may be the same for
determining the distances D10, D20.
The difference between the pre-resection distance D10 and the
post-resection distance D20 is given by distance D30, as seen in
FIG. 12B. The distance D30 represents the change in leg length that
resulted from the actual hip replacement procedure. This distance
D30 may then be compared with the pre-operatively calculated LLD.
In certain instances, where a hip replacement procedure was the
only planned procedure (i.e., a knee arthroplasty was not planned
for), the post-operative distance D30 may be compared with the
pre-operative value of LLD. If, for example, a surgeon desired to
correct a knee deformity that pre-operatively showed a 3 mm shorter
leg, a post-operative distance D30 change of 3 mm longer, for
example, may indicate that the hip replacement procedure was
successful in correcting LLD.
In certain instances, where a knee arthroplasty procedure is to
take place at a given time after the hip replacement procedure, the
distance D30 associated with a change in the proximal femur may be
one component of the overall LLD to be fixed. That is, the surgeon
may calculate or determine that the hip replacement procedure will
fix total LLD by a factor of X, and a subsequent knee replacement
procedure (e.g., to fix varus/valgus deformity) will fix total LLD
by a factor of Y, where X plus Y equals the total LLD.
In certain instances, a pre- and post-resection determination of
leg length may be determined without the aid of a femoral tracking
array. For example, as seen in FIG. 12C, which is a front view of a
right side of a pelvis 12, hip joint 10, femur 14, knee joint 17,
patella 19, fibula 21, and talus 604 prior to a hip replacement
surgery, a surgeon may calculate a pre-resection LLD as a distance
D40 between the pelvic tracking array 634 and a distal landmark
such as a distal aspect of the talus 638 or a distal aspect of the
tibia 640. As seen in FIG. 12D, which is a front view of a right
side of a pelvis 12, hip joint 10, femur 14, knee joint 17, patella
19, fibula 21, and talus 604 following a hip replacement surgery,
the surgeon may calculate a post-resection LLD as a distance D50
between the pelvic tracking array 634 and a distal landmark such as
a distal aspect of the talus 638 or a distal aspect of the tibia
640.
The difference between the pre-resection distance D40 and the
post-resection distance D50 is given by distance D60, as seen in
FIG. 12D. The distance D60 represents the change in leg length that
resulted from the actual hip replacement procedure. This distance
D60 may then be compared with the pre-operatively calculated LLD.
In certain instances, where a hip replacement procedure was the
only planned procedure (i.e., a knee arthroplasty was not planned
for), the post-operative distance D60 may be compared with the
pre-operative value of LLD. If, for example, a surgeon desired to
correct a knee deformity that pre-operatively showed a 3 mm shorter
leg, a post-operative distance D60 change of 3 mm longer, for
example, may indicate that the hip replacement procedure was
successful in correcting LLD.
In certain instances, where a knee arthroplasty procedure is to
take place at a given time after the hip replacement procedure, the
distance D60 associated with a change in the proximal femur may be
one component of the overall LLD to be fixed. That is, the surgeon
may calculate or determine that the hip replacement procedure will
fix total LLD by a factor of X, and a subsequent knee replacement
procedure (e.g., to fix varus/valgus deformity) will fix total LLD
by a factor of Y, where X plus Y equals the total LLD.
Instead of using the femoral tracking array (shown in FIGS.
12A-12B) the distal landmarks may be captured by the surgeon via a
digitizer or tracked navigation probe. For example, the surgeon may
place the distal tip of a tracked probe against a distal landmark
(e.g., distal aspect of tibia 640 or talus 638) and the location of
the landmark may be stored by the system 5. In this way, the
surgeon may capture or log the location of the distal landmark on
the patient's distal extremity pre- and post-hip replacement, and
the difference in the distance between the distal extremity and the
pelvic tracking array 634 may provide a difference in LLD as a
result of the surgical procedure. It is noted that the distal
aspects of the tibia and talus 640, 638 are exemplary and other
distal landmarks may be similarly employed without departing from
the scope of the present disclosure.
V. Example Computing System
Referring to FIG. 13, a detailed description of an example
computing system 1300 having one or more computing units that may
implement various systems and methods discussed herein is provided.
The computing system 1300 may be applicable to any of the computers
or systems utilized in the preoperative or intra-operative planning
of the arthroplasty procedure (e.g., registration, leg length
discrepancy), and other computing or network devices. It will be
appreciated that specific implementations of these devices may be
of differing possible specific computing architectures not all of
which are specifically discussed herein but will be understood by
those of ordinary skill in the art.
The computer system 1300 may be a computing system that is capable
of executing a computer program product to execute a computer
process. Data and program files may be input to the computer system
1300, which reads the files and executes the programs therein. Some
of the elements of the computer system 1300 are shown in FIG. 13,
including one or more hardware processors 1302, one or more data
storage devices 1304, one or more memory devices 1308, and/or one
or more ports 1308-1310. Additionally, other elements that will be
recognized by those skilled in the art may be included in the
computing system 1300 but are not explicitly depicted in FIG. 13 or
discussed further herein. Various elements of the computer system
1300 may communicate with one another by way of one or more
communication buses, point-to-point communication paths, or other
communication means not explicitly depicted in FIG. 13.
The processor 1302 may include, for example, a central processing
unit (CPU), a microprocessor, a microcontroller, a digital signal
processor (DSP), and/or one or more internal levels of cache. There
may be one or more processors 1302, such that the processor 1302
comprises a single central-processing unit, or a plurality of
processing units capable of executing instructions and performing
operations in parallel with each other, commonly referred to as a
parallel processing environment.
The computer system 1300 may be a conventional computer, a
distributed computer, or any other type of computer, such as one or
more external computers made available via a cloud computing
architecture. The presently described technology is optionally
implemented in software stored on the data stored device(s) 1304,
stored on the memory device(s) 1306, and/or communicated via one or
more of the ports 1308-1310, thereby transforming the computer
system 1300 in FIG. 13 to a special purpose machine for
implementing the operations described herein. Examples of the
computer system 1300 include personal computers, terminals,
workstations, mobile phones, tablets, laptops, personal computers,
multimedia consoles, gaming consoles, set top boxes, and the
like.
The one or more data storage devices 1304 may include any
non-volatile data storage device capable of storing data generated
or employed within the computing system 1300, such as computer
executable instructions for performing a computer process, which
may include instructions of both application programs and an
operating system (OS) that manages the various components of the
computing system 1300. The data storage devices 1304 may include,
without limitation, magnetic disk drives, optical disk drives,
solid state drives (SSDs), flash drives, and the like. The data
storage devices 1304 may include removable data storage media,
non-removable data storage media, and/or external storage devices
made available via a wired or wireless network architecture with
such computer program products, including one or more database
management products, web server products, application server
products, and/or other additional software components. Examples of
removable data storage media include Compact Disc Read-Only Memory
(CD-ROM), Digital Versatile Disc Read-Only Memory (DVD-ROM),
magneto-optical disks, flash drives, and the like. Examples of
non-removable data storage media include internal magnetic hard
disks, SSDs, and the like. The one or more memory devices 1306 may
include volatile memory (e.g., dynamic random access memory (DRAM),
static random access memory (SRAM), etc.) and/or non-volatile
memory (e.g., read-only memory (ROM), flash memory, etc.).
Computer program products containing mechanisms to effectuate the
systems and methods in accordance with the presently described
technology may reside in the data storage devices 1304 and/or the
memory devices 1306, which may be referred to as machine-readable
media. It will be appreciated that machine-readable media may
include any tangible non-transitory medium that is capable of
storing or encoding instructions to perform any one or more of the
operations of the present disclosure for execution by a machine or
that is capable of storing or encoding data structures and/or
modules utilized by or associated with such instructions.
Machine-readable media may include a single medium or multiple
media (e.g., a centralized or distributed database, and/or
associated caches and servers) that store the one or more
executable instructions or data structures.
In some implementations, the computer system 1300 includes one or
more ports, such as an input/output (I/O) port 1308 and a
communication port 1310, for communicating with other computing,
network, or vehicle devices. It will be appreciated that the ports
1308-1310 may be combined or separate and that more or fewer ports
may be included in the computer system 1300.
The I/O port 1308 may be connected to an I/O device, or other
device, by which information is input to or output from the
computing system 1300. Such I/O devices may include, without
limitation, one or more input devices, output devices, and/or
environment transducer devices.
In one implementation, the input devices convert a human-generated
signal, such as, human voice, physical movement, physical touch or
pressure, and/or the like, into electrical signals as input data
into the computing system 1300 via the I/O port 1308. Similarly,
the output devices may convert electrical signals received from
computing system 1300 via the I/O port 1308 into signals that may
be sensed as output by a human, such as sound, light, and/or touch.
The input device may be an alphanumeric input device, including
alphanumeric and other keys for communicating information and/or
command selections to the processor 1302 via the I/O port 1308. The
input device may be another type of user input device including,
but not limited to: direction and selection control devices, such
as a mouse, a trackball, cursor direction keys, a joystick, and/or
a wheel; one or more sensors, such as a camera, a microphone, a
positional sensor, an orientation sensor, a gravitational sensor,
an inertial sensor, and/or an accelerometer; and/or a
touch-sensitive display screen ("touchscreen"). The output devices
may include, without limitation, a display, a touchscreen, a
speaker, a tactile and/or haptic output device, and/or the like. In
some implementations, the input device and the output device may be
the same device, for example, in the case of a touchscreen.
In one implementation, a communication port 1310 is connected to a
network by way of which the computer system 1300 may receive
network data useful in executing the methods and systems set out
herein as well as transmitting information and network
configuration changes determined thereby. Stated differently, the
communication port 1310 connects the computer system 1300 to one or
more communication interface devices configured to transmit and/or
receive information between the computing system 1300 and other
devices by way of one or more wired or wireless communication
networks or connections. Examples of such networks or connections
include, without limitation, Universal Serial Bus (USB), Ethernet,
Wi-Fi, Bluetooth.RTM., Near Field Communication (NFC), Long-Term
Evolution (LTE), and so on. One or more such communication
interface devices may be utilized via the communication port 1310
to communicate one or more other machines, either directly over a
point-to-point communication path, over a wide area network (WAN)
(e.g., the Internet), over a local area network (LAN), over a
cellular (e.g., third generation (3G) or fourth generation (4G))
network, or over another communication means. Further, the
communication port 1310 may communicate with an antenna or other
link for electromagnetic signal transmission and/or reception.
In an example implementation, patient data, bone models (e.g.,
generic, patient specific), transformation software, tracking and
navigation software, registration software, and other software and
other modules and services may be embodied by instructions stored
on the data storage devices 1304 and/or the memory devices 1306 and
executed by the processor 1302. The computer system 1300 may be
integrated with or otherwise form part of the surgical system
100.
The system set forth in FIG. 13 is but one possible example of a
computer system that may employ or be configured in accordance with
aspects of the present disclosure. It will be appreciated that
other non-transitory tangible computer-readable storage media
storing computer-executable instructions for implementing the
presently disclosed technology on a computing system may be
utilized.
In the present disclosure, the methods disclosed herein, for
example, those shown in FIGS. 5 and 8, among others, may be
implemented as sets of instructions or software readable by a
device. Further, it is understood that the specific order or
hierarchy of steps in the methods disclosed are instances of
example approaches. Based upon design preferences, it is understood
that the specific order or hierarchy of steps in the method can be
rearranged while remaining within the disclosed subject matter. The
accompanying method claims present elements of the various steps in
a sample order, and are not necessarily meant to be limited to the
specific order or hierarchy presented.
The described disclosure including any of the methods described
herein may be provided as a computer program product, or software,
that may include a non-transitory machine-readable medium having
stored thereon instructions, which may be used to program a
computer system (or other electronic devices) to perform a process
according to the present disclosure. A machine-readable medium
includes any mechanism for storing information in a form (e.g.,
software, processing application) readable by a machine (e.g., a
computer). The machine-readable medium may include, but is not
limited to, magnetic storage medium, optical storage medium;
magneto-optical storage medium, read only memory (ROM); random
access memory (RAM); erasable programmable memory (e.g., EPROM and
EEPROM); flash memory; or other types of medium suitable for
storing electronic instructions.
While the present disclosure has been described with reference to
various implementations, it will be understood that these
implementations are illustrative and that the scope of the present
disclosure is not limited to them. Many variations, modifications,
additions, and improvements are possible. More generally,
embodiments in accordance with the present disclosure have been
described in the context of particular implementations.
Functionality may be separated or combined in blocks differently in
various embodiments of the disclosure or described with different
terminology. These and other variations, modifications, additions,
and improvements may fall within the scope of the disclosure as
defined in the claims that follow.
In general, while the embodiments described herein have been
described with reference to particular embodiments, modifications
can be made thereto without departing from the spirit and scope of
the disclosure. Note also that the term "including" as used herein
is intended to be inclusive, i.e. "including but not limited
to."
The construction and arrangement of the systems and methods as
shown in the various exemplary embodiments are illustrative only.
Although only a few embodiments have been described in detail in
this disclosure, many modifications are possible (e.g., variations
in sizes, dimensions, structures, shapes and proportions of the
various elements, values of parameters, mounting arrangements, use
of materials, colors, orientations, etc.). For example, the
position of elements may be reversed or otherwise varied and the
nature or number of discrete elements or positions may be altered
or varied. Accordingly, all such modifications are intended to be
included within the scope of the present disclosure. The order or
sequence of any process or method steps may be varied or
re-sequenced according to alternative embodiments. Other
substitutions, modifications, changes, and omissions may be made in
the design, operating conditions and arrangement of the exemplary
embodiments without departing from the scope of the present
disclosure.
* * * * *